Expandable shaft for securing and positioning slitter knives



March 16, 1965 H. G. WARREN ETAL 3,113,325

EXPANDABLE SHAFT FOR SECURING AND POSITIONING SLITTER KNIVES v 2 Sheets-Sheet 1 Filed Jan. 9, 1963 HoraceGJVarren HarryA.Kubiclc INVENTORS 3M l. MV-

' ATTIOHNES' United States Patent O 3,173,325 EXPANDABLE SHAFT 1103 SECURENG AND PGSITONWG 5121111112 lNl'/ES Y Horace G. Warren and Harry A. Kubick, Rochester, NEI., assignors to Eastman Kodak Company, Rochester, NX., a corporation of New Jersey Filed Jan. 9, 1963, Ser. No. 259,315 7 Claims. (Ci. SFF-439) This invention relates to a cutting arrangement and, more particularly, to an apparatus for accurately positioning slitter knives.

ln the art of web slitting, one of the accepted slitting mechanisms utilizes annular slitter knives which rotate while the web passes therebetween so that the web is divided into a plurality of narrower webs or strips. Many types of slitter knife arrangements are made adjustable to provide strip width control. One of the prior art arrangements utiiizes a clamp means which, although it does not damage the surface of the support shaft, often tends to skew the knives so that the clearances between the annular contacting surfaces vary about the periphery of the knife. Moreover, since the clamping means can be tightened variable amounts, the amount of skewing is dilllcult to predetermine because the relative position of each portion of the annular surface does not follow a predeterminable pattern. The use of various other locking arrangements may result in damage to the surface of the support shaft, whereby future adjustment of the knife position is made more diilicult. Because of this and related problems, a predetermined mating engagement of the cutting surfaces is most diillcult to predetermine.

Therefore, a primary object of the present invention is to provide a simple and reliable knife clamping arrangement.

A further object is to provide a knife clamping arrangement wherein the knives are movable along a shaft until such time as a fluid pressure within the shaft is increased to expand the hollow shaft and grip the knife blades.

A further object is to provide a knife clamping arrangement wherein the blades are brought into mating engagement after they are secured on their respective supports.

ln accordance with one embodiment of the present invention, we have provided a pair of parallel hollow shafts upon which are located a plurality of mating slitter knife blades. 'l'here is also provided an accurate Ipositioning means which will position the pairs of knives along the pair of shafts with a mating spacing of several thousandths of an inch. After all of the blades are so positioned, hydraulic pressure is applied internally of the shafts to expand the diameters of the shaft slightly. The flexibility of the shafts and the tolerances of the clearances involved are selected so that the knife blades will be gripped by the outer surface of the shaft before the blades attain a mating engagement. 1n accordance with one embodiment, the mating engagement is accomplished by having one bearing of each shaft floating, with the two bearings being at opposite ends of the pair of shafts, so that knife blades will move into engagement as the shafts expand longitudinally.

The subject matter which is regarded as our invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, as to its organization and operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. l is a plan view, partially in section, of one arrangement of the present invention;

FIG. 2 is a cross-sectional view taken along the lines of 2 2 of FIG. l to illustrate in more detail a positioning arrangement usable with the present invention; and

ice

FlG. 3 is a top plan view of the positioning arrangement shown in FIG. 2.

Referring now to the drawings, in which like numbers refer to similar parts, we have shown in FIG. l a rotatable pair of parallel knife support shafts 1li and 11. Mounted in a spaced-apart relationship on the upper shaft 10 is a plurality of annular cutter blades 12, and on the lower shaft 11 is a plurality of cutter blades 13 arranged to cooperate with the blades 12. The upper slitter blades 12 are provided with hard cutter surfaces 14 of chrome steel or the like with the hardness depending on the particular operating environment of the machine.

The shafts 1i) and 11 are resilient hollow cylindrical members of steel or the like, each defining therein a cavity 16 suitable for containing fluid pressures of the order or 2,000 p.s.i. These hollow cylindrical members are substantially rigid in response to bending moments developed by operation of the knife blades and are mounted on and sealed to end members 18 and 1Q. Each end member 13 is provided with a central passageway 20 through which fluid such as light grease or automotive brake iluid may be forced into the cavities 16. These passageways 20 are rotatably coupled to fittings 22 which are in turn coupled by conduits to a high pressure iluid source 24. The fluid pressure within the cavities 16 can be developed by a hydraulic jack, a pump, a screw or the like.

The end members 18 also serve to rotatably support the shafts 10 and 11 by means of journal bearings 25 and 26. As illustrated, bearings 25 are secured within the main bearings 27 to prevent longitudinal movement of the shaft 10. However, the bearings 26 are floating in the main bearings 27 and may move in accordance with the length of the shaft 11.V The end members 19, which also serve as gear-driven rotatable supports for the shafts 10 and 11, are supported in journal bearings 28 and 29 with the journal bearing 28 being floating so that the shaft 10 may expand in accordance with the pressure within its cavity 16. The main bearings 27, supporting the bearings 25 and 26, is mounted a fixed distance from main bearings 30 `supporting the bearings 28 and 29 on the machine frame or bedplate 32.

Also supported by the main bearings 27 and 30 and the bedplate 32 is a knife positioning carriage 34, shown more clearly in FIG. 2. The carriage 34 is slidably secured to a rigid guide shaft 36, which is in turn secured to the bedplate 32. The lateral location of the carriage 34 is controlled by a preloaded ball, nut and screw assembly with the drive screw being shown at 38.

In the specific example discussed herein, the knife blades 12 and 13 have their inner surfaces machined with about .0002 clearance compared to the minimum unpressurized diameter of their respective support shafts. Thus, they are relatively easily slidable along the shafts 10 and `11 when there is no pressure in the cavities 16. One acceptable method of positioning knife blades such as those illustrated at 12 and 13 is to drive the screw 38 from a controller 40 (FIG. l) using a stepping drive motor having up to 500 steps per revolution of the shaft 3S. With this arrangement, depending on the diameter and pitch of the threading on the shaft 38, the location of the carriage 34 can be controlled within about a thousandth of an inch. The upright position of the carriage 34 is determined by the effective rigidity of the shaft 36 and the tolerances of the sliding lit between the shaft 36 and the carriage 34. These tolerances are normally small, whereby the positioning of the knife blades 12 and 13, within .001 of the desired location, prior to `locking them to the shafts, may be expected.

The operation of the positioning carriage 34 is shown more clearly in FIG. 2, wherein the carriage has two pairs of grippers 43 and 44, with the grippers 43 being arranged to engage the cutter surface 14 and the grippers 44 B being arranged to engage the bl-ade 13. Positioning is accomplished by moving the carriage toward the right (in FIG. 1) sufficiently to place the grippers 43 and 44, respectively, behind a rst pair of movable knife blades. With the grippers in position, the controller itlis then operated to move the first pair of knife blades to the left as far as necessary to establish the desired spacing relative to the fixed bladesflZ and 13 for the particular cutting operati-on being set up. The positioning carriage 34 then again moves to the right sufficiently to grip a second pair of knife blades and is again returned to the control of the controller 40. Usually, the controller 40 will be control-led by punch tape or other automatic equipment which may accurately determine which revolution and which of the 500 radial positions of the shaft 3S is therproper one to position each pair of blades. As illustrated in FIG.2, the pairs of grippers 43 and 44 are raised and lowered to control engagement with the knife blades by a gear 46 and rack 47 drive arrangement, whic may be hand operated or operated under the control of a solenoid or motor 48. As shown more clearlyY in FIG. 3, the rack 47 is accurately guided by a rigid journal '49. Thus, rotation of a shaft 50 controls the vertical location of the grippers and rotation of the shaft 38 positions the pairs of blades. For reasons explained below, the settings of the pairs of blades is such that their mating surfaces are not in engagement, being separated about .003" in the example set forth.

Once all of the pai-rs of knife blades are accurately positioned by the positioning carriage 34, hydraulic pressure is applied from the fluid source 24 to the cavities 16. Thisrpressure slightly expands the diameter of the cylindrical shafts 10 and 11 to cause the outer surface of the shafts to engage tightly the inner surface of the knife blades. This pressure lit is, in many respects, similar to a shrink fit, e.g., the lblades being positioned while heated and allowed to cool and `shrink in place, except that the pressure in the cavities 16 may be e-asily Vreduced to remove the pressure t of the present invention. At the same time, because of the increased pressure within the cavities 16, the bearing 26 moves slightly toward the right (FIG. 1) -in the main bearings 27, and the bearing 28 moves slightly/'toward the left `in the main bearings 30. The spacing between the blades 12 and 13 during the positioning oper-ation is such that they do not contact each other until after they are secured by the pressure lit to the shafts. This prevents one rst seated from being able to dislocate its mating blade. Thereafter, the expansion of the shafts longitudinally with Athe floating bearings 26 and 28 Acauses the knife blades to engage to a preload of the order of .002" or .003 dependingon the particular type of Yknife blade being used, As will become apparent to those familiar with shrink fits and the like, the knife blades will not be appreciably skewed by their support pressures, so that their cutting edges will remain in flat plane, circular in shape. Because of this improved atness the overlapping preload overlap may be reduced to less than .001 for certain types of cutting act-ion. As is well known in cuttings of various sorts, such reduced pressures tend to reduce the wear of the cutting edge. A typical shaft might be designed to have a 2 inner diameter and 21/2 outer diameter of a material such as vmild steel that will expand 00044" when the pressure in the cavities 16 is .increased about 1,000 p.s.i. With a shaft of a length of the order of six feet, the longitudinal expansion thereof might be expected to be about .006H at pressures of 1,500 p.s.1.

Using this invention, since the gripping of the knife blades is accomplished throughout their entire inner periphery, no skewing forces are developed so that the cutting surfaces remain circular and the cutting engagement therebetween is uniform. Moreover, the blades can be repositioned many times without damage to the surfaces of the shafts 10 and 11.

CII

While we have shown and described particular embodiments of the present invention, other modifications may occur to those skilled in this art. For instance, the bearings 25 could also be made iioating with the preload mating pressure `being, provided by 1a fluid piston energized only after the blades are properly seated as described above. However, utilization of the natural longitudinal expansion of the shafts 10 and l1 is a preferred arrangement since it requires no additional parts. We intend, Jtherefore, to have the appended claims cover all modifications which fall within the true spirit and scope of our invention.

We claim:

1. A cutting arrangement comprising:

a pair of parallel rotatable shafts each having a minimum outer diameter and each defining a longitudinal fluidcontaining cavity therethrough;

ybearings supporting eac'h of said shafts and arranged so that said shafts may expand longitudinally relative to each other;

a plurality of pairs of slitter knife blades having inner diameters slightly greater than said minimum diameter and being positionable along said shafts throughout the region of the cavity;

means for positioning said pairs in a spaced-apart relationship such that they will mate only after longitudinal expansion of said shafts; and

means for increasing the uid pressure With-in the cavities to expand said shafts an amount suicient to develop a pressure fit between said lshafts and each of said knife blades and a mating engagement between each of said pairs of knife blades.

. A cutting arrangement comprising:

a pair of parallel rotatable shafts each having minimum outer diameters and each defining a longitudinal cavity therethrough;

bearings support-ing each of said shafts and being arranged with one float-ing bearing on one end of each shaft so that'said shafts may expand longitudinally relative to each other;

'a plurality of pairs of slitter knife blades having an inner diameter slightly greater than said minimum diameter and being positionable along said shafts throughout the region of the cavity and in a preselected spaced-apart relationship; and

means for increasing the fluid pressure within the cavities to expand said shafts in diameter an amount sufficient to develop a pressure fit between said shafts a-nd each of said knife blades and in length an amount sufficient to develop a preload mating engagement between each of said pairs of knife blades after they are individually secured by the pressure fit.

3. A cutting arrangement comprising:

-a pair of resilient parallel rotatable shafts having uniform outer diameters and each dening a longitudinal cavity therethrough;

bearings supporting each of said shafts and being arranged with a floating bearing at only one end of each shaft with the floating bearings being at opposite ends so that said shafts may expand longitudinally relative to each other;

`a plurality of pairs of slitter knife blades having an inner diameter slightly greater than said uniform diameter and being positionable along said pair of shafts throughout the region of the cavities during periods when fluid pressure in such cavity is minimum and being in a spaced-apart relationship so that said longitudinal expansion of said shafts will develop mating engagement between knife blades; and

means for increasing the uid pressure withinthe oavities to expand said shafts in diameter an amount sufficient to develop a pressure t between said shafts and each of said knife blades and to expand said shafts in length an amount sufficient to develop a preload mating engagement between each of said pairs of knife blades after they are indiuidually secured by the pressure iit.

4. A cutting arrangement comprising:

a pair of resilient parallel rotatable shafts each defining a longitudinal cavity therethrough;

bearings supporting each of said shafts and being arranged With one floating bearing on one end of each shaft with the floating bearings being at opposite ends so that said shafts may expand longitudinally relative to each other;

a pair of slitter knife blades `secured one to each of said shafts in a spaced-apart relationship so that said longitudinal expansion of said shafts will develop mating engagement between the knife blades;

and

means for increasing the fluid pressure within the cavities to expand -said shafts in length an amount sufcient to develop a preload mating engagement between said knife blades.

5. A cutting yarrangement comprising:

a pair of resilient shafts each defining a longitudinal cavity therethrough;

bearings supporting each of said shafts and being larranged so that said shafts may expand longitudinally;

a pair of slitter knife blades secured one to each of said shafts in a spaced-apart relationship; and means for increasing the uid pressure within said cavities to develop relative expansion of said shafts whereby said knife blades are placed in mating engagement.

6. A cutting arrangement comprising:

a pair of parallel hollow rotatable resilient shafts having a nominal minimum diameter;

bearings supporting each of said shafts and being arranged With -a floating bearing at opposite ends of said shafts to allow relative longitudinal expansion thereof;

a pair of slitter knife blades having an inner diameter slightly greater than said minimum diameter and being position-able along said pair of shafts during periods when fluid pressure therein is minimum and being in a spaced-apart relationship so that longitudinal expansion of said shafts will devel-op mating engagement between said knife blades; and

means for increasing the fluid pressure within said shafts sufficiently to developa pressure it between said shafts and each of said knife blades and in length an amount sufficient to develop a preload mating engagement between said pair of knife blades after they are individually secured by the pressure tit.

7. A cutting arrangement comprising:

a pair of parallel rotatable shafts each having a uniform minimum outer diameter and each defining a longitudinal fluid-containing cavity therethrough;

bearings supporting each of said shafts and arranged so that said shafts may expand longitudinaily relative to each other;

a pair of slitter knife blades one on each of said shafts having inner diameters slightly greater than said minimum'diameter and being positionable in proximity with each other over the region of each cavity respectively during reduced pressure thereof; and

means for increasing the fluid pressure Within the cavities to expand said shafts laterally for developing a pressure iit with each of said knife blades respectively and longitudinally for bringing said knife blades into mating engagement.

References Cited by the Examiner UNITED STATES PATENTS 2,318,838 5/43 Conradson 82-44 2,57 6,085 l l/ 51 Vivian 29-421 2,792,889 5/57 Kusel 83-501 2,797,602'l 7 57 Atherholt 827-44 3,073,198 1/63 Clem 83-665 FOREIGN PATENTS 1,03 8,902 9/5 8 Germany.

ANDREW R. IUHASZ, Primary Examiner. 

1. A CUTTER ARRANGEMENT COMPRISING: A PAIR OF PARALLEL ROTATABLE SHAFTS EACH HAVING A MINIMUM OUTER DIAMETER AND EACH DEFINING A LONGITUDINAL FLUID-CONTAINING CAVITY THERETHROUGH; BEARINGS SUPPORTING EACH OF SAID SHAFTS AND ARRANGED SO THAT SAID SHAFTS MAY EXPAND LONGITUDINALLY RELATIVE TO EACH OTHER; A PLURALITY OF PAIRS OF SLITTER KNIFE BLADES HAVING INNER DIAMETERS SLIGHTLY GREATER THAN SAID MINIMUM DIAMETER AND BEING POSITIONABLE ALONG SAID SHAFTS THROUGHOUT THE REGION OF THE CAVITY; MEANS FOR POSITIONING SAID PAIRS IN A SPACED-APART RELATIONSHIP SUCH THAT THEY WILL MATE ONLY AFTER LONGITUDINAL EXPANSION OF SAID SHAFTS; AND MEANS FOR INCREASING THE FLUID PRESSURE WITHIN THE CAVITIES TO EXPAND SAID SHAFTS ON AMOUNT SUFFICIENT TO DEVELOPE A PRESSURE FIT BETWEEN SAID SHAFTS AND EACH OF SAID KNIFE BLADES AND A MATING ENGAGEMENT BETWEEN EACH OF SAID PAIRS OF KNIFE BLADES. 